[RegAllocFast] Don't convert MCRegUnit to MCRegister. NFC (#123705)

Author: topperc

llvm/lib/CodeGen/RegAllocFast.cpp

@@ -688,7 +688,7 @@ void RegAllocFastImpl::reloadAtBegin(MachineBasicBlock &MBB) {
     if (PhysReg == 0 || LR.Error)
       continue;
 
-    MCRegister FirstUnit = *TRI->regunits(PhysReg).begin();
+    MCRegUnit FirstUnit = *TRI->regunits(PhysReg).begin();
     if (RegUnitStates[FirstUnit] == regLiveIn)
       continue;
 
@@ -758,7 +758,7 @@ bool RegAllocFastImpl::displacePhysReg(MachineInstr &MI, MCPhysReg PhysReg) {
 void RegAllocFastImpl::freePhysReg(MCPhysReg PhysReg) {
   LLVM_DEBUG(dbgs() << "Freeing " << printReg(PhysReg, TRI) << ':');
 
-  MCRegister FirstUnit = *TRI->regunits(PhysReg).begin();
+  MCRegUnit FirstUnit = *TRI->regunits(PhysReg).begin();
   switch (unsigned VirtReg = RegUnitStates[FirstUnit]) {
   case regFree:
     LLVM_DEBUG(dbgs() << '\n');